The present invention relates to an improved needle for multiple vacuum blood sample devices, of the type that pointed at both opposite ends to form two needles, fitted with relative covering elements, the first of which is designed to be introduced into the epidermis and vein, the second to be introduced into the closing stopper of a test tube, the needle in addition featuring, in what is substantially its central portion, an element for joining and retaining the covering element, and a threaded body, designed to engage in a corresponding hole centred in a test-tube carrying cylinder fitted with horizontally disposed tangs at either side to be gripped by the index and middle fingers of the user's hand.
As is well known in medical technique, blood samples for tests are taken using common syringes fitted with a hollow needle that draws the blood out of the vein.
Simple as these operations might seem when carried out by an expert, it is occasionally not so easy to introduce the needle without passing right through the vein, this making it necessary for the operation to be carried out again from the start.
The above happens as a result of the fact that the syringe will always take up a certain amount of space, obliging the operator to effect the injection and, above all, introduction into the vein, with a certain angle of incidence relative to the surface of the epidermis.
Syringes also exist that have an offset, or eccentric point for attachment needle: in such cases it is easier for the blood to be drawn out, but it can only be transferred to the test tube after the syringe has been withdrawn from the vein. However, more than one test will often be carried out, and it is thus necessary for several samples to be taken and divided between a similar number of test tubes. This forces one to use notably large syringes in order to take the necessary quantity of blood in one operation, and subsequently fill the single test tubes.
The problem of the angle of incidence of the needle, and that of taking multiple blood samples, are both solved by the use of a device composed of a test tube carrying cylinder, known as a holder, designed to receive vacuum test tubes, of a first needle, held at one end by a small pipe featuring two flexible diametrical tangs enabling it to be gripped by hand, and of a second needle, which can be connected to the other end of the small pipe by means of a LUER cone, and its point inserted in static fashion within the test tube holder. This second needle is fitted with a rubber cap that covers it. The test tubes are closed under vacuum with rubber stoppers that are less thick in their centre portion in order to facilitate their being pierced by the second needle. Using this device, it is possible to introduce the first needle into the vein, practically parallel to it, inasmuch as the space taken up by its diameter is almost negligible. It is then sufficient to place a test tube in the test tube carrying cylinder, pressing its stopper against the second needle which pierces it through the central zone of reduced thickness.
The full test can subsequently be replaced with another one without any problems, since the blood is retained by the cap of the second needle, which re-extends, completely covering the second needle, once the filled test tube has been removed.
A device constructed in this way reveals itself to be very practical in terms of ease of use, but has the disadvantage that there is a notable waste of valuable material -viz, the two needles, the LUER cone and small pipe, for every blood sample taken.
The greatest disadvantage, however, consists in the fact that the blood has to follow a long route from the vein to the test tube, with the possibility of minute clots being formed; these influence the results of the tests, above all in coagulationrelated tests such as the Quick time.
To eliminate these disadvantages, and above all that of the possible formation of small blod clots, consideration has been given to the use of double needles, that is to say, with two points, for introduction into the vein and introduction into the test tube stoppers respectively, fitted with a threaded element for connection to the test tube carrying cylinder, and featuring horizontally disposed tangs on which the index and middle fingers can locate and lay hold.
With this device, however, one gain has the problem of effecting a certain angle of inclination of the needle with respect to the epidermis.
The needle-epidermis angle problem also brings a functional problem in its wake, represented by the fact that, when in the vein, the point of the needle ends up being too close to the opposite wall of the vein. This means that, when the blood is being drawn out of the vein, this wall is also subjected to a certain amount of suction, such that it moves closer to and comes into contact with the point of the needle, and the operation of taking the blood sample is interrupted.
In this case, the provision of an offset, or eccentric connection for the test tube carrying cylinder cannot be contemplated, since the inner needle point (with cap) would not be able to pierce the centre portion of the test tube stopper, and piercing would be made difficult by the fact that the stopper wall is thicker.
In addition, there is another considerable problem: blood flows from the vein to the test tube at rather a high speed when using the vacuum test tube technique for taking blood samples, as a result of the difference in pressure between the two.
This speed is even higher at the start of the filling operation since, the vacuum being at its greatest, there is maximum suction. It is therefore possible on certain specific occasions, depending on the vacuum level in the test tubes, and the length of the tubes, for the outflowing blood to strike against the bottom of the test tube, creating the conditions for a phenomenon commonly known as blood stress to arise.
Amongst the morphological components of the blood, one has erythrocytes, which are known to be composed of round-shaped cells covered by a thin membrane, and having a red-orange colour as a result of the hemoglobin contained within them.
When subjected to a mechanical action provoking the break-up of the membrane, the hemoglobin flows out and, mixing with the plasma, changes its transparency characteristics, thus making the results of certain common clinical tests unreliable.
The object of the invention is to eliminate all the aforementioned disadvantages, avoiding the possibility of the above disadvantages occuring, under any circumstances, whilst making the operation of taking multiple blood samples from a patient both easy to carry out, convenient, and practical.